Absolute hardiness
by climate zone is extremely difficult to measure, because while two different
plants may succumb at temperatures below 32F, one may survive fine in winter
regions where temperatures regularly drop between 32-40F, while the other
may decline and eventually die if temperatures stay between 32-40F for more
than a few days. Nevertheless, knowing the absolute minimum temperature a
tropical/subtropical plant can tolerate can still be quite useful, so below
we have listed a number of plants, sorted by minimum climate zone.

Plants are
listed by USDA zone (click for more information),
with general winter temperature minimums. Also note that these are general
approximations, and within any species, individual plants can vary in hardiness.
Additionally, local microclimates can both virtually raise or lower a climate
zone. For example, Cocos nucifera, the coconut palm, generally will
not grow anywhere outdoors in the state of California, but in a few sheltered
locations-near buildings coconut palms can be grown outdoors.

If you live in Zone 9a for example, any plant listed in Zone 9a or lower is a candidate for your yard.